Braking control device

ABSTRACT

When a vehicle is stopped in an intersection by automatic emergency braking, secondary braking is prohibited in S 305 , a hazard lamp flashes in S 310 , and an idling stop is prohibited in S 320 . After it is determined in S 325  that the vehicle is stopped, when it is determined in S 330  that it is safe for the vehicle to start moving, stop maintenance braking is released in S 340.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of InternationalApplication No. PCT/JP2018/040803, filed Nov. 2, 2018, which claimspriority to Japanese Patent Application No. 2017-215149, filed Nov. 8,2017. The contents of these applications are incorporated herein byreference in their entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to braking control.

2. Related Art

There is a technique for avoiding the risk of a rear-end collision inwhich, when an idling stop is executed and the parking brake isactivated while a vehicle is stopped in an intersection, the parkingbrake is released and the vehicle is moved when it is determined thatthere is a risk of rear-end collision.

SUMMARY

An aspect of the technique according to the present disclosure is abraking control device, including: an operating unit that operatesautomatic emergency braking in response to detecting that an obstaclepresents in a traveling direction of a vehicle; a determining unit that,in a case where the vehicle is stopped in an intersection by theautomatic emergency braking, determines whether it is safer for thevehicle to continue being stopped, or safer for the vehicle to startmoving; and a safety ensuring unit that, in a case where the determiningunit determines that it is safer for the vehicle to start moving,releases the stopped state which was caused by the automatic emergencybraking.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram of a vehicle;

FIG. 2 is a flowchart illustrating a braking process;

FIG. 3 is a flowchart illustrating a determination process;

FIG. 4 is a diagram illustrating a state in which a vehicle is stoppedinside an intersection;

FIG. 5 is a graph illustrating a braking force by primary braking,secondary braking, and stop maintenance braking;

FIG. 6 is a graph illustrating a braking force by primary braking; and

FIG. 7 is a flowchart illustrating a safety ensuring process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

JP2008-121583A (Japanese Unexamined Patent Application Publication No.2008-121583) discloses a technique for avoiding the risk of a rear-endcollision in which, when an idling stop is executed and the parkingbrake is activated while a vehicle is stopped in an intersection, theparking brake is released and the vehicle is moved when it is determinedthat there is a risk of rear-end collision.

In the case of the background art described above, safety when thevehicle has stopped due to automatic emergency braking is notconsidered. In view of the above, it is an object of the presentdisclosure to improve safety while a vehicle is stopped in anintersection by automatic emergency braking.

An aspect of the technique according to the present disclosure is abraking control device, including: an operating unit that operatesautomatic emergency braking in response to detecting that an obstaclepresents in a traveling direction of a vehicle; a determining unit that,in a case where the vehicle is stopped in an intersection by theautomatic emergency braking, determines whether it is safer for thevehicle to continue being stopped, or safer for the vehicle to startmoving; and a safety ensuring unit that, in a case where the determiningunit determines that it is safer for the vehicle to start moving,releases the stopped state which was caused by the automatic emergencybraking. According to this embodiment, safety while a vehicle is stoppedin an intersection by automatic emergency braking is improved.

The above and other objectives, features and advantages of the presentdisclosure will be made more clear by the following detaileddescription, given referring to the appended drawings.

Embodiments of the present disclosure are described below with referenceto the drawings.

As illustrated in FIG. 1, a vehicle 30 includes a sensor group 11, acontrol device 20, a braking device 40, an internal combustion engine42, and a hazard lamp 45. The vehicle 30 is a self-driving car of level1 or higher. More specifically, the vehicle 30 has at least a functionof automatically performing braking.

The sensor group 11 includes a millimeter-wave radar 12, an image sensor14, a vehicle speed sensor 16, and a yaw rate sensor 18. Themillimeter-wave radar 12 emits a frequency-modulated radar wave in themillimeter wave band and measures the reflected wave. Themillimeter-wave radar 12 emits a millimeter wave toward a range that caninclude a target existing in front of the vehicle 30. The target is, forexample, another vehicle, a pedestrian, a bicycle, or the like. Thefront of the vehicle 30 includes right front and left front in additionto the front.

The image sensor 14 captures an image of the front of the vehicle 30.The imaging range of the image sensor 14 is a range that can include atarget existing in front of the vehicle 30. The vehicle speed sensor 16inputs the vehicle speed of the vehicle 30 to the control device 20.

A current location acquiring device 21 acquires the latitude andlongitude indicating the current location of the vehicle 30(hereinafter, simply referred to as the current location) and inputs theacquired latitude and longitude to a map information output device 23.The current location acquiring device 21 acquires the current locationusing a signal from a GPS satellite or the like.

The map information output device 23 inputs the map information at theinputted current location to the control device 20. When the currentlocation is near an intersection, the map information to be inputtedincludes information about the intersection. The information about theintersection includes information on how the roads intersect, thepresence or absence of a traffic signal, and the like.

The intersection in the present embodiment means an area where two ormore roads intersect, and means an area where a vehicle may travelacross an oncoming lane. Therefore, the intersection in the presentembodiment is not limited to a crossroad, but also includes a T-junctionand the like.

The internal combustion engine 42 is for example a gasoline engine. Thecontrol device 20 controls the rotation speed of the internal combustionengine 42. In a case where the vehicle speed is zero and a specifiedcondition such as the remaining capacity of the battery or the like issatisfied, the control device 20 executes an idling stop.

The braking device 40 includes a service brake and a parking brake. Theservice brake is operated when a driver steps on a brake pedal. Theparking brake is activated by a driver manually pulling up a brakelever. The service brake and the parking brake may be automaticallyoperated by the control device 20 in some cases.

The control device 20 includes a plurality of ECUs. The control device20 controls the components of the vehicle 30 described above.

The control device 20 repeatedly executes a braking process illustratedin FIG. 2 while the automatic braking function is set to ON.

The control device 20 first performs a determination process as S100.After the determination process is started, as illustrated in FIG. 3,the control device 20 determines whether at least a part of the vehicle30 is located within the intersection as S110. In the exampleillustrated in FIG. 4, the area J corresponds to the intersection. InS110 and in S120 next, information outputted from the current locationacquiring device 21 and the map information output device 23 is used.

In a case where YES is determined in S110, the control device 20proceeds to S120 and determines whether the current location is on anoncoming lane. Here, the oncoming lane means an area where an oncomingvehicle traveling straight ahead travels. Since S120 is based on thedetermination of YES in S110, in the example illustrated in FIG. 4, in acase where at least a part of the vehicle 30 is located in the area J1,YES is determined in S120. FIG. 4 illustrates a case where a part of thevehicle 30 is located in the area J1.

In a case where YES is determined in S120, the control device 20proceeds to S130 and determines whether an oncoming vehicle isprohibited from traveling straight ahead. More specifically, it isdetermined whether the right arrow of an arrow traffic signal to befollowed by the host vehicle is lit up green. In Japan, when the rightarrow of an arrow traffic signal to be followed by the host vehicle islit up green, the signal to be followed by the oncoming vehicle isoperated so as to prohibit travel straight ahead. FIG. 4 illustrates astate in which the right arrow is lit up green on the arrow trafficsignal S to be followed by the host vehicle.

In a case where NO is determined in S130, the control device 20 proceedsto S140 and sets the flag to ON. The flag being ON indicates that, whena vehicle is stopped inside an intersection when automatic emergencybraking is activated, it is safer for the vehicle to start moving thanto continue being stopped. Automatic emergency braking is also referredto as collision avoidance braking.

The term “safe” as used here means the level of probability of collisionwith an oncoming vehicle that is traveling straight ahead. Stopping inthe present embodiment means a state where the vehicle speed is zero. Ina situation where YES is determined in S110 and S120 and NO isdetermined in S130, there is a high probability that a collision willoccur if the vehicle 30 continues to be stopped and the oncoming vehicletraveling straight ahead does not avoid the collision.

When NO is determined in any of S110 and S120, or when YES is determinedin S130, the control device 20 proceeds to S150 and sets the flag toOFF. In other words, in these cases, when the vehicle is stopped in acase where automatic emergency braking is operated, it is safer tocontinue being stopped than for the vehicle to start moving.

When the flag is set, the control device 20 proceeds to S160, whichdetermines whether the situation is such that automatic emergencybraking should be operated. The control device 20 executes S160 based oninput from the millimeter-wave radar 12 and the image sensor 14. In acase where NO is determined in S160, the control device 20 returns toS110. In a case where YES is determined in S160, the control device 20terminates the determination process and proceeds to S210.

After proceeding to S210, the control device 20 executes primarybraking. Primary braking is braking with a braking force G1 illustratedin FIG. 5 and FIG. 6 as an upper limit. Here, the braking force is aparameter having a correlation with the deceleration (m/s′) when thevehicle 30 is traveling. However, in the present embodiment, the brakingforce may be controlled even in a case where the vehicle speed of thevehicle 30 is zero. In this case, the braking force is a parameter notrelated to the deceleration.

The control device 20 proceeds to S220 while executing primary braking,and determines whether the flag is set to ON. In a case where the flagis set to OFF, the control device 20 proceeds to S230 and determineswhether secondary braking is necessary. Secondary braking is brakingwith the braking force G2 illustrated in FIG. 5 as the upper limit ofthe braking force. The braking force G2 is larger than the braking forceG1.

In a case where the risk of a collision with an obstacle ahead isavoided by primary braking before the vehicle speed becomes zero, thecontrol device 20 determines that secondary braking is unnecessary. Inthis case, the control device 20 proceeds to S250 at the timing when thevehicle speed becomes zero.

On the other hand, when it is determined that secondary braking isnecessary, the control device 20 executes secondary braking. The controldevice 20 proceeds to S250 at the timing when the vehicle speed becomeszero. In FIG. 5, the timing at which the vehicle speed becomes zero isindicated as being time t1.

After proceeding to S250, the control device 20 changes the brakingforce to the braking force Gh, and maintains the braking force Gh for aspecified time T1. The operation of maintaining the braking force at thebraking force Gh is also called a stop maintenance braking. In thepresent embodiment A, the parking brake is used for stop maintenancebraking. While stop maintenance braking is continued, the vehicle 30does not start to move even when stepping on the accelerator pedal.After S250 terminates, the control device 20 repeats the braking processfrom S100.

On the other hand, in a case where the flag is ON, the control device 20proceeds to S300 and executes a safety ensuring process.

As illustrated in FIG. 7, after the safety ensuring process is started,the control device 20 prohibits secondary braking as S305. Continuing,the control device 20 causes the hazard lamp 45 to flash as S310. Thisreduces the risk of a rear-end collision by a following vehicle.

Next, the control device 20 proceeds to S320 and prohibits an idlingstop. Subsequently, the control device 20 proceeds to S325 anddetermines whether the vehicle has stopped. In the present embodiment,in a case where automatic emergency braking is operated while the flagis ON, braking by primary braking is executed until the vehicle stops.S325 is repeatedly executed until the vehicle stops.

After it is determined that the vehicle has stopped, the control device20 proceeds to S330 and determines whether it is safe for the vehicle tostart moving. The term “safe” as used herein means that there is nolonger a risk of colliding with an obstacle that has caused automaticemergency braking to operate even when the vehicle starts to move. In acase where there is a risk of colliding with an obstacle when thevehicle starts to move, S330 is repeatedly executed. While S330 is beingrepeated, stop maintenance braking is continued.

When it is determined that it is safe for the vehicle to start moving,the control device 20 proceeds to S340 and releases stop maintenancebraking. Idling stop is prohibited, so the vehicle 30 will start movingwhen the accelerator pedal is depressed.

FIG. 6 illustrates an example in which, at the time the vehicle isstopped at time t2, it is determined that it is safe even when thevehicle starts moving. Therefore, stop maintenance braking is notperformed. In this case, S340 is substantially not performed.

The control device 20 then proceeds to S350 and prohibits automaticemergency braking. The control device 20 then proceeds to S360 and turnsOFF the hazard lamp 45. The control device 20 then proceeds to S370,which determines whether the vehicle has exited the intersection. Thecontrol device 20 repeats S370 until it is determined that the vehiclehas exited the intersection.

When it is determined that the vehicle has exited the intersection, thecontrol device 20 terminates the safety ensuring process. After that,the control device 20 proceeds to S410 and releases the prohibition ofautomatic emergency braking. Continuing, the control device 20 proceedsto S420 and releases the prohibition of the idling stop. After S420, thecontrol device 20 repeats the braking process from S100.

According to the embodiment described above, the safety when the vehiclestops within an intersection due to automatic emergency braking isimproved. In a situation where the vehicle is stopped in an intersectionand on the oncoming lane, and a signal allows an oncoming vehicle topass through the intersection by going straight ahead, there is a riskthat the vehicle will collide with the oncoming vehicle if the vehiclecontinues to be stopped. In such a situation, it is more likely thatquickly passing through the intersection will be safer. In the presentembodiment, in order to realize such an operation, stop maintenancebraking is terminated in the shortest possible time in the abovesituation.

In the situation described above, by prohibiting secondary braking, therisk of being hit by a following vehicle is reduced, and this preventsthe stopped position of the vehicle from deviating from the originalroute due to the occurrence of skidding which was caused by secondarybraking, making it possible to turn right smoothly.

The correspondence between the embodiments and the claims will bedescribed. The control device 20 corresponds to a braking controldevice, S100 and S220 correspond to a determining unit, S210 and S240correspond to an operating unit, and S300 corresponds to a safetyensuring unit.

The present disclosure is not limited to the embodiments, examples, andmodifications of the present description, and may be implemented byvarious configurations without departing from the gist of the presentdisclosure. For example, the technical features in the embodiments,examples, and modifications corresponding to the technical features ineach embodiment described in the summary of the invention section arefor solving some or all of the problems described above, or in order toachieve some or all of the effects described above, replacement andcombination may be made as appropriate. Technical features that are notdescribed as essential in this description may be deleted asappropriate. For example, the following example is given.

The embodiments describe left-hand traffic as an example; however, theembodiments may also be applied to right-hand traffic. In the case ofright-hand traffic, replacement may be performed as appropriate. Forexample, a right turn is replaced with a left turn, and a right arrow isreplaced with a left arrow.

In the embodiments described above, some or all of the functions andprocesses realized by software may be realized by hardware. Moreover,some or all of the functions and processes realized by hardware may berealized by software. As the hardware, for example, various circuitssuch as integrated circuits, discrete circuits, or a circuit module orthe like combining those circuits may be used.

What is claimed is:
 1. A braking control device, comprising: an operating unit that operates automatic emergency braking in response to detecting that an obstacle presents in a traveling direction of a vehicle; a determining unit that, in a case where the vehicle is stopped in an intersection by the automatic emergency braking, determines whether it is safer for the vehicle to continue being stopped, or safer for the vehicle to start moving; and a safety ensuring unit that, in a case where the determining unit determines that it is safer for the vehicle to start moving, releases the stopped state which was caused by the automatic emergency braking.
 2. The braking control device according to claim 1, wherein the determining unit determines that it is safer for the vehicle to start moving in a case where, as a prerequisite condition, the vehicle is stopped on an oncoming lane.
 3. The braking control device according to claim 1, wherein the determining unit determines that it is safer for the vehicle to start moving in a case where, as a prerequisite condition, a traffic signal allows oncoming vehicles to pass straight ahead through the intersection.
 4. The braking control device according to claim 1, wherein the safety ensuring unit, in a case where the vehicle is stopped in an intersection by automatic emergency braking, causes a hazard lamp to flash.
 5. The braking control device according to claim 1, wherein the safety ensuring unit, in a case where the automatic emergency braking is operated in an intersection, prohibits secondary braking.
 6. The braking control device according to claim 1, wherein the safety ensuring unit, in a case where the vehicle is stopped in an intersection by automatic emergency braking, prohibits idling stop until the vehicle exits the intersection.
 7. The braking control device according to claim 1, wherein the safety ensuring unit, in a case where the vehicle is stopped in an intersection by automatic emergency braking, prohibits the automatic emergency braking until the vehicle exits the intersection. 